Background art for high pressure metal halide arc discharge lamps is shown in U.S. Pat. No. 3,761,758 and the patents listed therein. Said patents disclose lamps having a double-ended arc tube, that is to say, an elongated arc tube having an electrode at each end. Our invention is particularly concerned with low wattage metal halide lamps; such lamps are discussed in U.S. Pat. No. 4,161,672 which also discloses the use of double-nded arc tubes therefor.